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xfs: Correctly lock inode when removing suid and file capabilities 

Currently XFS calls file_remove_privs() without holding i_mutex. This is
wrong because that function can end up messing with file permissions and
file capabilities stored in xattrs for which we need i_mutex held.

Fix the problem by grabbing iolock exclusively when we will need to
change anything in permissions / xattrs.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
hifive-unleashed-5.1
Jan Kara 2015-05-21 16:05:56 +02:00 committed by Al Viro
parent 45f147a1bc
commit a6de82cab1
1 changed files with 10 additions and 1 deletions
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11
fs/xfs/xfs_file.c
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@ -563,6 +563,13 @@ restart:
if (error)
return error;
/* For changing security info in file_remove_privs() we need i_mutex */
if (*iolock == XFS_IOLOCK_SHARED && !IS_NOSEC(inode)) {
xfs_rw_iunlock(ip, *iolock);
*iolock = XFS_IOLOCK_EXCL;
xfs_rw_ilock(ip, *iolock);
goto restart;
}
/*
* If the offset is beyond the size of the file, we need to zero any
* blocks that fall between the existing EOF and the start of this
@ -623,7 +630,9 @@ restart:
* setgid bits if the process is not being run by root. This keeps
* people from modifying setuid and setgid binaries.
*/
return file_remove_privs(file);
if (!IS_NOSEC(inode))
return file_remove_privs(file);
return 0;
}
/*